I just wanted to add this both for I and anyone that may be looking for a reason as to why this is happening. What I am talking about is a color looking very bland and faded when rendering in Mental Ray. What causes this is the Gamma fields being incorrect. To fix this problem you simply have to add a Utility Gamma shader before inserting your bitmap. So here's what I am talking about and how it's done.
To the left you can see what I am talking about. The ball on the left is faded and not the same as the one on the right, the correct color. Again it's just a simple shader that you can add to correct this. Just before you add your bitmap to your diffuse layer make sure to add the 'Utility Gamma & Gain (mi)' as shown to the right. By adding this it will color correct you to the correct intensity. Wood looking dull? Add the Gamma and Gain shader! Red's looking pink> Add the Gamma and Gain shader! It instantly places your Gamma at a 2.2 setting. From the best I can tell from reading it's almost always the correct setting. I haven't read much that says you should change it. But by adding this shader you will correct your texture like the image above of the 2 red balls.
Need another way to do this? Maybe you need the entire scene to be corrected and you don't want to place this into your texture stack every time? Well you can go into your 'Preferences' tab and do this as well. By activating this you will turn your Gamma settings on in the same way that you did when adding it just before your bitmap is in place! One thing I noticed when doing this is every time I open Max up it would have the settings still the same as I left it. So if I activated the Gamma then when I opened Max it still would be and in the new scene I'm working on everything may be rendering incorrectly now. So just keep in mind when using this way of correcting your Gamma settings!
1 year ago